As a matter of fact, I have him in my database (don't know exactly why, at the moment). I agree with your wife (wives) information.
Dr. Thomas Arnold Callen (1818-1856) was a son of William Callen (1794-1860) who hailed from Cabarrus Co. NC and settled in Dallas Co. AL. William married Sarah "Sallie" O. Littleton (1801-1870) in 1816 in Cabarrus Co. NC. William was a son of James Callen (1770-1842) who married Olivia H. Stewart. James died on February 20, 1842 at Summerfield in Dallas Co. AL. James was a son of William Callen (1735-1815) who married Elizabeth Taylor (1740-1810)
in 1761 in Loudoun Co. VA. Elizabeth was a daughter of Henry and Susan Taylor.

I have that Dr. Thomas A. Callen had a daughter (Mary Eliza Callen, maybe Mary Elizabeth Callen) by his wife Diana Mildred Smith. Mary Eliza Callen (1851-1929) married William Henry Purcell (1845-1910) in 1870. William was born in Robeson Co. NC and he died in Columbia, AL (which is in Houston County).

NOW I can tell you why these folks are in my database.
William and Mary had a daughter Selma Purcell (1874-1947) who married john Daniel Abernathy, Sr. (1870-1948) in 1898 in Columbia (Houston County), AL at the M. E. Church there. John was a deputy solicitor in Chambers Co. AL in 1898 (I think that has something to do with the federal judicial system; please tell me more, if you know). John was a son of Samuel Henry Harrison Abernathy (1845-1931) who married Mary Ann Malissa Slay. Samuel died at Roanoke in Randolph Co. AL and he is buried at Mt. Hickory (aka Old Hickory, I think, could be adjacent cemeteries) Cemetery in Chambers Co. AL. Mary Ann was a daughter of Nathan Slay and Mary Ann Brock (1810-1884). Samuel was a son of John Davis Abernathy, Sr. (1820-1854)--his wife was Margaret Priscilla Baker--who was a brother of my Great-Grandfather Abernathy (buried at Macedonia Primitive Baptist Cemetery in Chambers Co. AL, same place where their father Samuel Abernathy is buried). I have lots more on the ABERNATHY (my maiden name) line, if you need it.

Selma Purcell had a sibling Wyllie Callen Purcell (b 1872, gender unknown to me). Selma had a sister Ruby Estelle Purcell (b 1876) who married John Floyd Collina. Selma had a brother Thomas Malcolm Purcell (b 1879). Selma had a sister Florence Purcell (1880-1917). Selma had a brother Clarence "Clare" Purcell who married Ida West.

I hope these data are useful to you. Was Dr. Thomas Arnold Callen a physician? Did he get around by railroad or horseback (or both)? I have that his other wife was
Margaret Elvira wiley (1817-1842) who was born (and died) in Dallas Co. AL. Their wedding was on August 17, 1841 in Dallas Co. AL. I have that Margaret and the doctor celebrated their first wedding anniversary, and then she was dead less than three weeks later (September 4, 1842).
I have that his wedding to Diana Mildred Smith occurred on November 19, 1846 in Sumner Co. TN.